2056 Journal of Applied Microscopy 



plants. Might this process indicate some relation of the ancestors of Vaucheria 

 to the Volvocaceae ? 



10. Make a diagram in the notes, showing the life cycle of Vaucheria. 

 (See Fig. 5.) 



11. In the notes, make diagrams of the two gametes of Sphaerella, Par- 

 dorina, Eudorina, and Volvox, and describe how these may indicate stages in the 

 evolution of perfectly developed oospheres and spermatozoids. 



Fig. .5 — Life cycle of Vaucheria. 



12. Note. — The oosphere and spermatozoid are highly specialized cells, 

 the first representing nutritive qualities, the second the active qualities. A 

 union of the two must result in a very perfect reproductive cell. The develop- 

 ment of sexual individuals is along the same lines as indicated in the sexual 

 cells, and the development of one sex or the other is dependent largely on 

 a favorable or an unfavorable food environment. Male or female sex is not an 

 inherited quality, but depends on the environment present during the germina- 

 tion of the spore and the development of the embryo, and it can be directly con- 

 trolled in many cases by artificial means. 



TWO PECULIAR COENOCYTIC COLONIES. 



XIX. Fediasfrum boryanum (Turp.) Menegh. Order, Hydrodictyales. 

 Family, Hydrodictyaceae. 



This beautiful alga is found along with other species of the same genus in 

 the sediments at the bottom of ponds, creeks, etc. It is a flat colony of cells 

 which develop into coenocytes. 



1. Mount some of the sediment containing Pediastrum in water and study 

 under high power. Draw two of the plate-shaped colonies — one with eight 

 ccenocytes and one with sixteen. Notice the difference between the marginal 

 coenocytes and those in the interior. Note also the chloroplast and one or more 

 large pyrenoids. 



2. Look for colonies in which the cells in each coenocyte have separated, 

 preparatory to the formation of a new colony. 



3. Draw a colony in which some of the ccenocytes are empty, each empty 

 shell having a slit-like opening through which the daughter colony escaped. 



Ohio State University. JOHN H. SCHAFFNER. 



